Communications Technology Handbook, 2nd Edition

3 Audio signal processing

The quality of audio communications is chiefly governed by the originating sound level, system distortion and background noise levels (see also Noise, p. 232, and TV sound channels, p. 386). For telephony, there are the added problems associated with echoes and round-trip delays. The primary aim of all audio processing is therefore to maximise the system signal to noise (S/N) ratio. This, like power levels, is usually quoted in decibels (dB) and is a convenient unit because the human ear can just about recognise a change in sound level of 1 dB. Since noise in all its forms is a destroyer of information and proportional to bandwidth, it is important to ensure that the system bandwidth is restricted to that which is just ...